The use of negative film strips in backlighted message directories is well known. Such strips are formed by conventional photographic techniques and typically bear a name or other item of information which appears as transparent lettering on a substantially opaque background. It is also well known to use an array of film strip holders for placement of the film strips therein. These holder arrays, in turn, are backlighted to allow light to pass through the holders and through the transparent portions of the film strips being held.
In the past, it has been the practice to provide a message directory having a fixed vertical array of film strip holders, or segments of fixed vertical arrays, for holding a number of strips in place. While the film strips are able to be inserted into the holders interchangeably, the film strip holders themselves are fixed and unable to be interchanged with other holders in the array. Those types of message directories have several disadvantages. For example, when a single film strip is required to be added to or withdrawn from the array, it is necessary to disassemble the entire array of strips by removing each individual film strip and placing the strip in its new position in another adjacent holder. Another disadvantage with such an array is the fact that the film strips must be handled again subsequent to initial placement of them in the holders. Because of their thin composition, the films are subject to becoming misplaced, wrinkled or broken when handled. An example of such holders may be seen in U.S. Pat. No. 4,653,209 to Cobb.
Another type of directory currently available uses individual and interchangeable strip holders. These holders are typically comprised of two piece injection molded plastic parts that snap together. Each individual piece is molded to a precise size and must be matched with a mating piece. These types of message directories also have several disadvantages which are similarly difficult to overcome. For example, the injection molded parts are relatively expensive to tool. Also because each holder must have a relatively large opening disposed in it to permit light to pass through a substantial portion of the film strip held by it, these film holders tend to suffer from a lack of strength sufficient to protect the films or to prevent the holders themselves from unsnapping or breaking. For an example of such holders see U.S. Pat. No. 4,021,951 to Vanostrand.